The present invention relates to an improved manhole cover lifting tool. More specifically, the invention relates to a lever-type manual tool for lifting and maneuvering manhole covers of various sizes away from respective manholes, wherein a freely slidable sleeve mounted on the lever permits a virtually infinite range of adjustments of the distance between the fulcrum and the sleeve, thereby enabling the tool to be used with any size manhole cover while maximizing the available leverage.
There are a number of manhole cover lifting devices disclosed in the prior art. For example, in U.S. Pat. No. 4,076,217, a lever is combined with scissors-type lifting means for lifting a manhole cover and pivoting the raised cover away from the manhole in a horizontal plane.
In U.S. Pat. No. 4,181,290, a lever-type manhole cover lifting tool is combined with a hydraulic jack, hydraulic cylinder, or pulley cable to facilitate lifting of the cover and thereafter pivoting the cover away from the manhole.
In U.S. Pat. Nos. 4,482,182; 2,846,259; 2,832,628; and 2,086,318, manually operated lever-type lifting tools are disclosed in which one or more points of attachment for a member connected to the manhole cover are fixed along the length of the lever. In the '259 and '628 patents, flexible chains are connected between the selected, fixed points of attachment on the lever and lifting elements attached to the manhole cover. However, because the attachment points are fixed, the chain must be adjustable in length to accommodate manhole covers of different diameter This arrangement is unsatisfactory since it is not possible to maximize leverage, and additional hardware is often required to insure secure attachment of the chain links to the various fixed points of attachment.
Manhole cover diameters are typically 22", 24" or 26". Increasingly, however, even larger manhole covers of up to 30" diameter are being utilized, particularly to facilitate ingress and egress of personnel into the manhole. Accordingly, there is a need for a manhole cover lifter tool which is simple and easy to use, which maximizes leverage, and which accommodates all of the above manhole cover sizes.
The present invention provides a simplified and easily manipulable tool for lifting manhole covers of various diameters and which allows the user to maximize available leverage.
In one exemplary embodiment, the invention includes an elongated lever having one free end which comprises a handle, and another free end which comprises a working end, to which is attached a first tool head. The tool head itself is provided with a pair of alternatively useable manhole cover lifting tools. The choice of lifting tool is determined by the shape of an aperture or slot typically provided in manhole covers for lifting purposes. A second tool head is provided at one end of a flexible chain and includes alternatively usable tools substantially identical to those of the first tool head. The chain is attached at its other end to a sleeve which is slidably mounted on the lever. In the present invention, the flexible chain has a single, fixed, length, i.e., the length is not intended to be adjusted for manhole covers of different diameter. Rather, the freely slidable sleeve performs the function of adapting the device to manhole covers of different diameters while at the same time, permitting maximum leverage to be applied during lifting.
In the present invention, the manhole cover lifting tools are first engaged within the appropriate slots, apertures or the like provided in the manhole cover, with the sleeve being adjusted along the length of the lever to the extent necessary to allow attachment of one of the lifting tools of the second tool head to the manhole cover. Thereafter, the sleeve may be slidably adjusted along the length of the lever until the chain is taut and the lever is at an angle of inclination which is most comfortable for the user, and/or which maximizes the available leverage, i.e., by moving the sleeve as far as possible toward the fulcrum.
Once the lifting operation has commenced, the sleeve frictionally binds against the lever, and effectively prevents any further sliding movement of the sleeve during the lifting operation.
In a further aspect of the invention, the unused tool fixed to the first tool head at the working end of the lever serves as the fulcrum point by which the manhole cover is lifted and subsequently pivoted substantially horizontally away from the manhole.
Further objects and advantages of the present invention will become apparent from the detailed description of the invention which follows below.